This is concretion with  natural double of two uncommon trilobite species:

-Ectillaenus katzeri (Barrande, 1872)

The specimen was found in Traversot fm., Middle Ordovician (Darriwilian) deposits, south of Rennes , Brittany, France. Reconstruction 0%. Shipping worldwide $20.  



On Dec-22-14 at 03:47:49 PST, seller added the following information: